more *m files

Hi there

apologizes for the banal question, but I am new to Matlab and unfortunately I have to require a kind, but quick help.

I'd like to understand following topic.
I have a main function in matlab, let's call it

main.m

Into this function there is a call to other functions, let call them
son.m
son1.m

Question: is it enough to put them in the same folder or shall I link them some how with the same matlab ?

Apologizes but I have not been able to find this apparently simple hint.

Thanks in advance for your help.